1. Field of the Invention
The present invention relates to a valve unit which opens a channel at a predetermined time so that a fluid can flow along the channel, and an apparatus having the same.
2. Description of the Related Art
For example, a valve unit includes a microchannel forming a path for a fluid is formed in a chip used in a biochemical reaction such as a polymerase chain reaction (“PCR”). The chip is formed of glass or silicon. The valve unit blocks the microchannel so that a biochemical fluid cannot flow through the microchannel and opens the microchannel at a certain time to cause the fluid to flow.
FIG. 1 is a plan view of a conventional valve unit 10, which is disclosed in Anal. Chem. Vol. 76, pp. 1824-1831, 2004.
Referring to FIG. 1, the conventional valve unit 10 includes a microchannel 12 which forms a path for a fluid (F), a paraffin wax 20 which blocks the microchannel 12 so that the fluid (F) cannot flow through the microchannel 12, and a wax chamber 15, which is disposed adjacent to the paraffin wax 20 and has an extended channel width compared to a channel width of microchannel 12. Heat (H) is applied to the paraffin wax 20 at a certain time allowing a flow of the fluid (F). When the paraffin wax 20 is molten and the microchannel 12 is opened due to the heat (H), the fluid (F) which has been in a non-circulating state, flows in a direction of an arrow (that is, from upwards to downwards) indicated at a bottom portion of the wax chamber 15. The molten paraffin wax 20 is condensed again in the wax chamber 15 and does not disturb the flow of the fluid (F).
However, in the conventional valve unit 10, a large amount of time is required to melt the paraffin wax 20 by heating. It is difficult to precisely control a time for opening the microchannel 12, and a heating unit for melting the paraffin wax 20 should be directly provided on a substrate 11 on which the microchannel 12 is formed. For example, it is difficult to make the valve unit 10 small. When directly providing the heating unit on the substrate 11, there is a difference in thermal conductivity according to a material used in forming the substrate 11, which causes a difference in precision for opening the microchannel 12. Thus, when plastics are used to reduce costs for manufacturing a chip used in a biochemical reaction, the thermal conductivity of plastics is much lower than that of glass or silicon of the chip. As such, precision in opening the microchannel 12 is lowered.